Sheet folding apparatus and image forming apparatus

Abstract

A sheet folding apparatus is disclosed, including a conveying roller pair; first and second folding roller pairs; first and second sheet detecting units; first and second sheet guiding members, a sheet conveyed from the conveying roller pair is guided to the first or second folding roller pair, a sheet edge is detected by the first or second sheet detecting unit, a sheet conveying direction and a sheet conveying distance are controlled based on the detected result, timings of an operation of the first or second sheet guiding member and conveying of the sheet by the first and second folding roller pair are aligned, and the sheet is folded while being placed by the first or second folding roller pair therebetween.

The invention claimed is: 
     
       1. A sheet folding apparatus, comprising:
 a conveying roller pair configured to feed a sheet; 
 a first roller pair configured to fold the sheet fed from the conveying roller pair; 
 a second folding roller pair configured to fold the sheet fed from the conveying roller pair in conjunction with the first folding roller pair which is in an opposing manner and at a predetermined gap therewith; 
 a first sheet detecting unit configured to detect a sheet edge on the first folding roller pair side and a second sheet detecting unit configured to detect a sheet edge on the second folding roller side, the first sheet detecting unit and second sheet detecting unit being outside an opposing area of the first folding roller pair and the second folding roller pair; 
 a first sheet guiding member configured to guide the sheet fed by the conveying roller pair to the first folding roller pair; and 
 a second sheet guiding member on the side opposing the first sheet guiding member and configured to guide the sheet fed by the conveying roller pair to the second folding roller pair, wherein: 
 the first and second sheet guiding members are substantially parallel when the sheet is fed by the conveying roller pair; 
 the first sheet guiding member and the second sheet guiding member are operated in accordance with a specified sheet folding scheme, the sheet conveyed from the conveying roller pair is guided to the first folding roller pair or the second folding roller pair, a sheet edge is detected by the first sheet detecting unit or the second sheet detecting unit, a sheet conveying direction and a sheet conveying distance are controlled based on the detected result, timings of the operation of the first sheet guiding member or the second sheet guiding member and conveying of the sheet by the first folding roller pair and the second folding roller pair are aligned, and the sheet is folded while being placed by the first folding roller pair or the second folding roller pair therebetween, and 
 the sheet folded portion is detected by the first sheet detecting unit or the second detecting unit and in accordance with control of the sheet conveying direction and the sheet conveying distance based on the detected result, the sheet folded portion for which folding was performed by the first folding roller pair or the second folding roller pair is guided to either of the first folding roller pair and the second roller pair that are arranged in an opposing manner, the sheet folded portion is detected by the first sheet detecting unit or the second detecting unit and the sheet conveying direction and the sheet conveying distance is controlled based on the detected result, timings of the operation of the sheet guiding member and conveying of the sheet by the first folding roller pair and the second folding roller pair are aligned, and the sheet is folded while being placed by the first folding roller pair or the second folding roller pair therebetween. 
 
     
     
       2. The sheet folding apparatus as claimed in  claim 1 , wherein, when the sheet folded portion is guided from one of the first folding roller pair and the second folding roller pair to one opposing the one of the first folding roller pair and the second folding roller pair, the first sheet guiding member which is operable to guide it to the first folding roller pair and a second sheet guiding member which is operable to guide it to the second folding roller pair which is arranged on the side opposing the first sheet guide member are used to place therebetween faces before and after the sheet folded portion such that they are not apart from each other. 
     
     
       3. The sheet folding apparatus as claimed in  claim 2 , wherein, in an operation of the first sheet guiding member and the second sheet guiding member when the sheet folded portion is guided from one of the first folding roller pair and the second folding roller pair to the opposing one of the first folding roller pair and the second folding roller pair, the second sheet guiding member operates when the sheet folded portion is guided from the first folding roller pair to the opposing second folding roller pair and the first sheet guiding member operates when it is guided from the second folding roller pair to the opposing first folding roller pair. 
     
     
       4. The sheet folding apparatus as claimed in  claim 2 , wherein the operation of the first sheet guiding member and the second sheet guiding member when the sheet folded portion is guided from one of the first folding roller pair and the second folding roller pair to the opposing one of the first folding roller pair and the second folding roller pair is an operation intended for a target position, so that it is stopped after reaching the target position. 
     
     
       5. The sheet folding apparatus as claimed in  claim 4 , wherein
 the target position of the first sheet guiding member or the second sheet guiding member is located between a waiting position before an operation in which a tip of the sheet is guided from the conveying roller pair to the first folding roller pair or the second folding roller pair and a stop position after an operation in which the tip of the sheet is guided from the conveying roller pair to the first folding roller pair or the second folding roller pair. 
 
     
     
       6. The sheet folding apparatus as claimed in  claim 4 , wherein
 an operation target position of the first sheet guiding member or the second sheet guiding member is arranged to be changeable in accordance with conditions of temperature/moisture, a type of the sheet, or whether there is a reentry into the conveying roller pair of the sheet tip due to a folding length of the sheet. 
 
     
     
       7. the sheet folding apparatus as claimed in  claim 2 , wherein
 the operation of the first sheet guiding member and the second sheet guiding member when the sheet folded portion is guided from one of the first folding roller pair and the second folding roller pair to the opposing one of the first folding roller pair and the second folding roller pair is an operation which makes a reentry of the sheet tip into the conveying roller pair smooth. 
 
     
     
       8. The sheet folding apparatus as claimed in  claim 7 , wherein a starting reference position of an operation of the first sheet guiding member or the second sheet guiding member is a position at which the first sheet detecting unit or the second sheet detecting unit is installed. 
     
     
       9. The sheet folding apparatus as claimed in  claim 8 , wherein the starting reference position of the operation of the first sheet guiding member or the second sheet guiding member is arranged outside the opposing area of the first folding roller pair and the second folding roller pair and is a position at which are installed a first sheet detecting unit which detects a sheet edge on the first folding roller pair side and a second sheet detecting unit which detects a sheet edge on the second folding roller pair side. 
     
     
       10. An image forming apparatus having an image forming unit which forms an image onto a sheet, comprising the sheet folding apparatus as claimed in  claim 1 . 
     
     
       11. The sheet folding apparatus of  claim 1 , wherein the first and second sheet guiding members are located inside an area defined by outside boundaries of the conveying roller pair.